I. Field of the Invention:
This invention relates generally to a code converting system and more specifically to an electronic, digital system particularly adapted for use in video display apparatus for selectively changing the location on the screen where graphic information is to be displayed.
II. Description of the Prior Art:
So-called video games have become highly popular in the recent past. In such machines, video signals are usually formed by synthesizing program-information which is recorded in a read-only memory along with information which is generated by the players as well as other information which may be required.
In a video game machine, especially wherein the video screen is disposed in a generally horizontal orientation such as on a table top, it is often required that the display be inverted so that players on opposite sides of the table may be provided with an identical display as far as its orientation on the screen is concerned. For exemplary purposes only, consider the situation of a baseball game. When the screen is disposed in a vertical orientation, and each player is facing the screen, each simultaneously perceives the same display of the field. However, when the screen is disposed in a horizontal orientation, as in a table top, and the players are seated on opposite sides of the table one will be observing the game from the outfield towards home plate whereas the other player will be viewing it from home base toward the outfield. As they play the game, they will be repeating the interchanges of batting and fielding and, hence, it is desirable that the video presentation be inverted as the players change from a batting mode to a fielding mode.
One prior art approach at providing this desired inversion of the video presentation has involved the use of two separate memories having recorded contents symmetric with respect to one another. As the mode of play is to be reversed, the contents of the first memory are read into the second and the contents of the second memory are read into the first. This requires an inordinate amount of circuitry and associated programming.